1. Field of the Invention
The present invention relates to films made from vinylidene chloride polymers or copolymers, especially films suitable for the packaging of food products, such as meat. More specifically, the present invention relates to films having a poly(vinylidene chloride) layer that acts as an O.sub.2 -barrier.
2. Background Information
Thermoplastic packaging films made of vinylidene chloride copolymer, often referred to as "saran" or "PVDC", have been used for the packaging of food products (e.g., fresh and processed meats) as well as a variety of other items.
Multilayer films including at least one layer containing PVDC have been produced by coextrusion, lamination, and extrusion coating. Oriented, heat-shrinkable films comprising PVDC also have been produced. Vinylidene chloride has been copolymerized with vinyl chloride, methyl methacrylate, and/or other suitable copolymers. Stabilizers and HCl scavengers have been blended with PVDC.
Nevertheless, provision of a PVDC composition capable of providing a packaging film with a lower O.sub.2 -transmission rate (OTR), so that a lesser amount of the PVDC composition is needed to provide the desired O.sub.2 -barrier property, would be desirable. Provision of a PVDC composition having an improved thermal stability, so that the composition has less tendency to degrade during extrusion, also would be desirable. Provision of a molten PVDC composition which can be extruded at higher speeds also would be desirable. Finally, provision of a PVDC composition having a reduced stickiness to processing equipment would also be desirable. Such a composition would tend to reduce disruptions during extrusion caused by degradation of PVDC in the extruder, which necessitates purging and/or cleaning of the extrusion system.